How Do I Choose The Gear Ratio For a Speed Reducer?

Speed reducers are a very important part of mechanical power transmission systems. There are several different types available, each with certain features. Installing the wrong gear reducer into an application can be disastrous. The first step to choosing a gear reducer is to know what torque and speed are required as well as the most suitable motor to use. Next, if a gear reducer is needed, you select the proper type and ratio.

So what is a speed reducer? Usually, the benefits are that it can reduce speed and increase torque. The amount of speed reduction will depend on the type of motor used. For example, while one motor might not need a gear reducer to run at low speeds (as low as 1,000 rpm or so), another may need one to run at any speed.

For speed reducers, the gear ratio is calculated using the equation below. G is the gear ratio, and N is the angular velocity of the motor and the load.



Speed reducers multiply the torque output of a motor. For this reason, a smaller, less expensive motor with a gear reducer may be the right decision for your application than a larger motor without one. To calculate the required gear ratio when torque multiplication is needed, use this equation: G is the gear ratio, T is torque and e is efficiency.


Another function of gear reducers is reducing the reflected load inertia to the motor by a factor of the square of the gear's ratio. For most motion applications, the reduction of reflected inertia from motors is ideal. This is especially true for high-performance applications but is applicable for any motion application. Rather than only considering the gear's ratio, you should also take into account the inertia of the load and the motor. To achieve perfect inertia matching, take the square root of the ratio of motor inertia to load inertia. G is the gear ratio and J is the inertia of the motor and load.




About Sumitomo Drive Technologies

At Sumitomo Drive Technologies, we work hand-in-hand with our customers to ensure that their industrial gearboxes, speed reducers, and accessories remain operational for years to come. Many of our products have been in high-speed and harsh environments for years. Clients make the switch to Sumitomo to experience that durability and decrease the amount of unscheduled downtime and maintenance in their facility. We ensure that every unit we design or repair leaves our Unites States' facilities quickly to keep your application up and running. Please call us at 1.800.762.9256 or contact us by email to receive a quote for your facility or information about our industrial gearbox repair services. We will be glad to tell you more about our products and connect you to a representative in your area.


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